Psoriasis is a long-lasting autoimmune disease characterized by raised areas of abnormal skin. These areas are typically red, or purple on some people with darker skin, dry, itchy, and scaly. Psoriasis varies in severity from small, localized patches to complete body coverage. Injury to the skin can trigger psoriatic skin changes at that spot, which is known as the Koebner phenomenon.

The least common type of psoriasis, erythrodermic psoriasis can cover your entire body with a red, peeling rash that can itch or burn intensely. Psoriatic arthritis. Psoriatic arthritis causes swollen, painful joints that are typical of arthritis.

Psoriasis is a genetically programmed inflammatory disease that primarily affects the skin in about 3% of individuals in the United States. Psoriasis is characterized by skin cells that multiply up to 10 times faster than normal. When these cells reach the surface and die, raised, red plaques covered with white scales form.